SLR Cameras

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  1. 1. SLR CameraAperture, lens, viewfinder, ISO, shutter and ways to load andunload film.1
  2. 2. ApertureReferred to the lens diaphragm opening inside a photographic lens. The size ofthe diaphragm opening in a camera lens REGULATES amount of light passesthrough onto the film inside the camera.Aperture size is usually calibrated in f-numbers or f-stops. i.e. those littlenumbers engraved on the lens barrel like f22 (f/22),16(f/16), f/11, f/8.0, f/5.6, f/4.0, f/2.8, f/2.0, f/1.8 etc. Each of this valuerepresents one time the amount of light either more or less in quantity.Meaning to say, f/16 will let in 1X the amount of light than a diaphragmopening of f/22 and so forth; while on the other hand, an aperture of f/4.0 willlet in 1X lesser than that of f/2.8 etc. 2
  3. 3. Aperturef1.2f2f2.8f16f22f323
  4. 4. LensLENS ELEMENTS & IMAGE QUALITY All but the simplest cameras contain lenses which are actuallycomprised of several "lens elements." Each of these elementsdirects the path of light rays to recreate the image as accurately aspossible on the digital sensor. The goal is to minimizeaberrations, while still utilizing the fewest and least expensiveelements.4
  5. 5. ViewfinderThe viewfinder is the single most important user interface on any camera.Throughout the history of cameras, the method of aiming the cameraaccurately and communicating its view to the operator is what has determinedand defined most different basic camera types.Now, if you were no expert and just taking a stab at this, youd probably guessthat you would want to see in the viewfinder all of the picture youre about totake. It stands to reason you dont want to see half of it, or a tenth of it, sowhy wouldnt you just want to see all of it? As with many things, however, itturns out that the uncomplicated answer is not the correct one.One might reasonably ask, whats the point of using an SLR at all if you stillcant see what the lens sees?Try to buy a camera with at least a 95% viewfinder. Even this modest standardis tough to meet these days, but theyre out there. 97% or 98% is better, butgood luck. 5
  6. 6. ViewfinderThe manufacturers would just as soon keep you in the dark about thedifferences between good and bad viewfinders. But you cant shoot well if youcant see what youre shooting, or if your camera is only giving you anapproximate idea what youll get on film. Know your viewfinder!This diagram shows the light path in a typical 35mm SLR6
  7. 7. ViewfinderA cutaway view of the familiar 35mm SLR viewing system. You can clearly seethe lens, the mirror, and the glass pentaprism. The screen is the flat piece justabove the mirror; the eyepiece is the bit furthest to the right, where your eyepeers into the whole thing.7
  8. 8. ISO In traditional (film) photography ISO (or ASA) was the indication of howsensitive a film was to light. It was measured in numbers (youve probablyseen them on films 100, 200, 400, 800 etc.). The lower the number thelower the sensitivity of the film and the finer the grain in the shots youretaking. In Digital Photography ISO measures the sensitivity of the image sensor. Thesame principles apply as in film photography the lower the number theless sensitive your camera is to light and the finer the grain. Higher ISOsettings are generally used in darker situations to get faster shutter speeds(for example an indoor sports event when you want to freeze the action inlower light) however the cost is noisier shots. Ill illustrate this below withtwo enlargements of shots that I just took the one on the left is taken at100 ISO and the one of the right at 3200 ISO (click to enlarge to see the fulleffect).ISO (International Organization for Standardization)8
  9. 9. ShutterWhat is shutter speed ? The aperture diaphragm of a lens (bigger or smallervalues) AND timing (open and close) of the cameras shutter curtain - BOTH perform the tasks of regulating the amount of light entering thecamera and expose onto the film. The shutter speed scales engraved on theshutter speed dial of conventional camera bodies with a shutter speed ring ORvia some flickering digital numerals on the LCD screen like:1/8000, 1/4000, 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2,1 or -1, -2 etc. are essentially indicators of the duration (timing) at which theshutter curtain opens up and closes during an exposure process.9
  10. 10. ShutterModern AF cameras, with a wealth of sophisticated features incorporatedwithin, are more complicated, as shown is a full featured LCD screen.Substituting all conventional mechanical dial and levers by computer circuits.So, gone are the traditional shutter dial or ring on the camera. Highlighted partrepresents usual location (generally big and bolder numerals or figures) of thedigitally displayed shutter speeds OR aperture values.10
  11. 11. Film 11